The building of roads is a science that has existed for hundreds of years. Men smoothed down dirt for roadbeds and later MacAdam invented a roadbed material which bears his name. During the course of paving of roads, and driveways and other areas wherein cementitious materials are employed, it is often necessary to determine the slope of the incline of such road or path. Spirit levels and slope indicators have existed in the prior art for determining such slope measurements. One such slope indicator is one particularly adopted for use with railroad tracks. Name that of Misz, as disclosed in U.S. Pat. No. 2,304,313. Spirit levels and grading levels are employed for the determining of a level line between different points or any rise or fall between spaced points. The inventor is aware of U.S. Pat. Nos. 808,862 and 1,805,004 which are invented for inclination measurement. In the construction of modern day physical improvements it often becomes necessary to determine or establish certain values of inclination of slope for various elements that comprise the improvement. For example, in the construction of buildings inclination values must be established for roofs, sloping floors, ramps, sidewalks, and drain pipes etc. In the construction of pavement areas such as highways, airports, and parking lots it is customary to the art to shape the various pavement surfaces to certain values of inclination as may be specified by various governing regulations and design. Hereto a slope indication means may be employed.
It is believed that there are no devices in the prior art which are capable of providing inclination values with the same accuracy and sensitivity, length of span between points of measurement, total range of inclination measurement, and versability that the device of this application provides.
It has been found, that due to the inability of workmen to quickly and accurately determine slopes and grades on the job while work is in progress that final slopes and grades often do not meet specified regulations and design. This can result in poor drainage of pavement areas, rough riding highways, pipes, sidewalks and roofs which do not slope properly, etc. In addition, many hours and expense required of expensive survey crews who are commonly hired to gather topographical data can be saved since spot checking of slopes and grades by one person utilizing the device of this invention would provide sufficient data.
Currently available spirit levels, such as Starratt.RTM. number 133 series have a flat base plate of only about one foot in length. It is difficult to measure accurately, inclination average values over long distances, in view of the short length of the item employed. Most other engineers and paving contractor's levels similarly have a flat sole plate extending the length of the instrument, said sole plate being of one to two feet in length.
In contrast however, the invention of this application does not have a flat sole plate, but legs at both ends such that an average value can be taken to compensate for minor inconsistencies over short spatial intervals. In addition, the device of this invention can measure slope over a larger span of distance. In one embodiment, the standard length is 6 feet of span distance. By a simple folding step the unit converts from the 6 foot standard length to a 3 foot length for slope measurement in more compact areas.
Accuracy, sensitivity, durability and simplicity are extremely important in an adjustable spirit level of any kind, for in many instances the inclination values to be dealt with are very small and the instrument will likely be subjected to rough treatment.